Bandil (Hive Bee)
02-04-03 03:19
No 404335
      Dean Stark trap with nitropropene/styrene prep.  Bookmark   

Some time ago, swim enquired about the preparation of relative pure 2,5-dimethoxy-betanitropropene. I believe Rhodium suggested the use of a dean stark trap, if the nitroethane was not 100% anhydrous. According to the original preparation of the nitropropene:

A solution of 10.0 g 2,5-dimethoxybenzaldehyde in 50 mL glacial acetic acid was treated with 6.8 g of nitroethane and 4.0 g of anhydrous ammonium acetate.


AFAIK a Dean stark trap works by separating the water that is distilled azetropically with the solvent. But, in this case the water is soluble in the solvent acetic acid. How could a DS trap be used here? Even with nitroethane as the solvent, it could not work, as the nitroethane has a weigth of 1.05 g/mL and would thus form the lower layer...

Any ideas on how to get this scheme to work?

regards
Bandil
 
 
 
 
    Xicori
(Newbee)
02-04-03 03:21
No 404336
      it should work to just substitute the GAA with  Bookmark   

it should work to just substitute the GAA with Toluene or Benzene - but im not completely sure on that, but it works with P2NP...


lg
xicori
 
 
 
 
    Bandil
(Hive Bee)
02-04-03 03:48
No 404341
      Do you have any references on that reaction?  Bookmark   

Do you have any refernces on that reaction?
 
 
 
 
    Antoncho
(Official Hive Translator)
02-04-03 06:07
No 404363
      Do it in toluene.  Bookmark   

There's a proc on Rh's for o-methoxy-P2P.

Also TFSE will give you Barium's excellent proc for hard-to-make nitropropenes and nitrobutenes.


Antoncho
 
 
 
 
    Rhodium
(Chief Bee)
02-04-03 13:00
No 404459
      ethylenediamine diacetate  Bookmark   

I suggested the use of 0.1 equiv. ethylenediamine diacetate in IPA at RT for 24h, gives 50% yield of pure nitropropene, the same yield as the ammonium acetate procedure in Pihkal but with less work. Directions can be found in edda.html at my page.
 
 
 
 
    hest
(Hive Adickt)
02-05-03 13:16
No 404808
      Henry  Bookmark   

Use benzene as solven and KF/ethylenediamine diacetate /Am.Formiat/cyclohexylamin/ect. as the catalyst then let the DeanStarc work 24houers.
Byt the synt of 2,5-dimetho... in a mw. works so nice, why bother onyething else. For some off the other aldehydes it's a different history.